The only problem with that shaft is that the motor requires me to use collet type prop adaptor, so I would have to grind a spot for the C clip and re-grind a spot for the grub screw for the bell housing.

Yes, I can do that.
So I should skip the extension arms?
Based on the pictures I see in the various large Skywing threads, most do not use any extensions. Is it because the control surfaces are large enough?

Personally I would use them.They were out of stock when I ordered so I bodgied up some home made ones for the ailerons.I am getting just enough throw on elevator without them,rudder probably doesn't need them.
The thing is though,I am driving my ele and ail servos at or near 150% travel adjust which is apparently not that good for them or so I've heard.
I would like some more elevator throw also,so with my next purchase I will get some.Thing is,you can always dial the throws back or use dual rates,but you are mechanically limited to the max throw by the length of your servo horn.
You may not want or need the throw now,but trust me you will later.
My advice,get them and futureproof your setup.You dont even have to use the outermost hole,but it is there for future wildness!
Bleary.

I tried the ailerons without extension arms and even at 140% throw I was only getting about 30-35 deg. I found that on 3s and 13x6.5 prop in hover and trying to counter the torque that I just didn't have enough aileron to counteract.

As soon as I got the throw up to 45 deg it was no problem.

Having only recently moved from sport flying into learning 3D, I would look at these big ailerons and assume you don't need big throws for big effect. That is correct, at flight speed. 3D is a lot of the time below stall speed and that makes a huge difference to how the surfaces respond.

I misunderstood your post. Thought you were saying using dual rates will be good enough. I will be more than happy to use the extensions and dial them down initially. Feda's got the screws on the way to me.

The supplied X-mount (combo) don't line up with the pre-drilled holes on the firewall and the pre-drilled holes don't seem centralised too. Can't find an alternative X-mount in the LHS. Did you guys have this issue as well?

The supplied X-mount (combo) don't line up with the pre-drilled holes on the firewall and the pre-drilled holes don't seem centralised too. Can't find an alternative X-mount in the LHS. Did you guys have this issue as well?

The pre-drilled holes will not line up because of the built-in right thrust offset. Once a motor and propeller is mounted the propeller will be close to centralised.

After a few smashes and ripping out and re-glueing the fire wall it will all seem so funny looking back.

You don't need to be too precise with these things. Just take it out and fly the crap out of it.

As to the servo arm extensions. Without them the plane will fly ok and even 3D ok. More throw is always better as you get more skills.

I was like you, my first few flight I thought, ' hell these ailerons have a lot of throw and the roll rate is fast'. Then down at 3D speed, I was saying, 'I wish I could get more throw out of those ailerons'.